Stylistic

Colloquial language is not necessarily a grammatical and stylistic questionable form of expression. There is no doubt a cultivated variety of it which I really find to my liking.

What he writes apart from his sentences is understandable, though full of errors and stylistic flaws. But when he tackles writing his example sentences, it's just incomprehensible bullshit.

In my opinion, whether to use a comma before la, after la, or to not use a comma at all is a personal stylistic choice.